Amplification Element Research Articles

Ultrasensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V(2+) conjugates.

A novel, enhanced photoelectrochemical immunoassay was established for sensitive and specific detection of carbohydrate antigen 19-9 (CA19-9, Ag). In this protocol, TiO2 nanowires (TiO2NWs) were first decorated with Au nanoparticles to form TiO2NWs/Au hybrid structure, and then coated with CdSe@ZnS quantum dots (QDs) via the layer-by-layer method, producing TiO2NWs/Au/CdSe@ZnS sensitized structure, which was employed as the photoelectrochemical matrix to immobilize capture CA19-9 antibodies (Ab1); whereas, bipyridinium (V(2+)) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V(2+) conjugates, which were used as signal amplification elements. The TiO2NWs/Au/CdSe@ZnS sensitized structure could adequately absorb light energy and dramatically depress electron-hole recombination, resulting in evidently enhanced photocurrent intensity of the immunosensing electrode. While target Ag were detected, the Ab2@V(2+) conjugates could significantly decrease the photocurrent detection signal because of strong electron-withdrawing property of V(2+) coupled with evident steric hindrance of Ab2. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V(2+) conjugates, the well-established photoelectrochemical immunoassay exhibited a low detection limit of 0.0039 U/mL with a wide linear range from 0.01 U/mL to 200 U/mL for target Ag detection. This proposed photoelectrochemical protocol also showed good reproducibility, specificity and stability, and might be applied to detect other important biomarkers.

Sensitive electrochemical detection of telomerase activity using spherical nucleic acids gold nanoparticles triggered mimic-hybridization chain reaction enzyme-free dual signal amplification.

We report an electrochemical sensor for telomerase activity detection based on spherical nucleic acids gold nanoparticles (SNAs AuNPs) triggered mimic-hybridization chain reaction (mimic-HCR) enzyme-free dual signal amplification. In the detection strategy, SNAs AuNPs and two hairpin probes were employed. SNAs AuNPs as the primary amplification element, not only hybridized with the telomeric repeats on the electrode to amplify signal but also initiated the subsequent secondary amplification, mimic-hybridization chain reaction of two hairpin probes. If the cells' extracts were positive for telomerase activity, SNAs AuNPs could be captured on the electrode. The carried initiators could trigger an alternative hybridization reaction of two hairpin probes that yielded nicked double helices. The signal was further amplified enzyme-free by numerous hexaammineruthenium(III) chloride ([Ru(NH3)6](3+), RuHex) inserting into double-helix DNA long chain by electrostatic interaction, each of which could generate an electrochemical signal at appropriate potential. With this method, a detection limit of down to 2 HeLa cells and a dynamic range of 10-10,000 cells were achieved. Telomerase activities of different cell lines were also successfully evaluated.

Micro-channel plates and vacuum detectors

A micro-channel plate is an array of miniature electron multipliers that are each acting as a continuous dynode chain. The compact channel structure results in high spatial and time resolutions and robustness to magnetic fields. Micro-channel plates have been originally developed for night vision applications and integrated as an amplification element in image intensifiers. These devices show single-photon sensitivity with very low noise and have been used as such for scintillating fiber tracker readout in high-energy physics experiments. Given their very short transit time spread, micro-channel plate photomultiplier tubes are also being used in time-of-flight and particle identification detectors. The present paper will cover the history of the micro-channel plate development, basic features, and some of their applications. Emphasis will be put on various new manufacturing processes that have been developed over the last few years, and that result in a significant improvement in terms of efficiency, noise, and lifetime performance.

Label-free colorimetric aptasensor for sensitive detection of ochratoxin A utilizing hybridization chain reaction

The combination of high selectivity of aptamer with the peroxidase-mimicking property of DNAzyme has presented considerable opportunities for designing colorimetric aptasensor for detection of ochratoxin A (OTA). The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. Hybridization chain reaction (HCR) between two hairpin DNAs was employed to further improve the sensitivity of this method. The presence of OTA triggers the opening of the hairpin structure and the beginning of HCR, which results in the release of many DNAzyme, and generates enhanced colorimetric signals, which is correlated to the amounts of OTA with linear range between 0.01 to 0.32nM, and the limit of detection is 0.01nM under optimal conditions. OTA in yellow rice wine and wheat flour samples was also detected using this method. We demonstrate that a new colorimetric method for the detection of OTA has been established, which is simple, easy to conduct, label-free, sensitive, high throughput, and cost-saving.

Ultrasensitive photoelectrochemical immunoassay for matrix metalloproteinase-2 detection based on CdS:Mn/CdTe cosensitized TiO2 nanotubes and signal amplification of SiO2@Ab2 conjugates.

An ultrasensitive photoelectrochemical sandwich immunoassay was developed to detect matrix metalloproteinase-2 (MMP-2, antigen, Ag) based on CdS:Mn/CdTe cosensitized TiO2 nanotubes (TiO2-NTs) and signal amplification of SiO2@Ab2 conjugates. Specifically, the TiO2-NTs electrode was first deposited with CdS:Mn by successive ionic layer adsorption and reaction technique and then further coated with CdTe quantum dots (QDs) via the layer-by-layer method, forming TiO2-NTs/CdS:Mn/CdTe cosensitized structure, which was employed as a matrix to immobilize capture MMP-2 antibodies (Ab1); whereas, SiO2 nanoparticles were coated with signal MMP-2 antibodies (Ab2) to form SiO2@Ab2 conjugates, which were used as signal amplification elements via the specific antibody-antigen immunoreaction between Ag and Ab2. The ultrahigh sensitivity of this immunoassay derived from the two major reasons as below. First, the TiO2-NTs/CdS:Mn/CdTe cosensitized structure could adequately absorb the light energy, dramatically promote electron transfer, and effectively inhibit the electron-hole recombination, resulting in significantly enhanced photocurrent intensity of the sensing electrode. However, in the presence of target Ag, the immobilized SiO2@Ab2 conjugates could evidently increase the steric hindrance of the sensing electrode and effectively depress the electron transfer, leading to obviously decreased photocurrent intensity. Accordingly, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 3.6 fg/mL and a wide linear range from 10 fg/mL to 500 pg/mL for target Ag detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising platform for the detection of other important biomarkers.

Linking glucose oxidation to luminol-based electrochemiluminescence using bipolar electrochemistry

The range of potential analytes for bipolar electrochemistry can be significantly extended by modification of bipolar electrodes with enzymatic biosensing layers. In this study, we employed a Prussian blue-based glucose detection system involving electrochemical reduction of enzymatically generated hydrogen peroxide at the cathodic pole. The concentration of glucose in solution can be correlated with oxidative luminol electrochemiluminescence at the opposite anodic pole, which was recorded with a photomultiplier tube. This opens a route for novel analytical systems using glucose oxidase as an amplification element for the reporter reaction.

Enhanced Photoelectrochemical Strategy for Ultrasensitive DNA Detection Based on Two Different Sizes of CdTe Quantum Dots Cosensitized TiO2/CdS:Mn Hybrid Structure

A TiO2/CdS:Mn hybrid structure cosensitized with two different sizes of CdTe quantum dots (QDs) was designed to develop a novel and ultrasensitive photoelectrochemical DNA assay. In this protocol, TiO2/CdS:Mn hybrid structure was prepared by successive adsorption and reaction of Cd(2+)/Mn(2+) and S(2-) ions on the surface of TiO2 film and then was employed as matrix for immobilization of hairpin DNA probe, whereas large-sized CdTe-COOH QDs and small-sized CdTe-NH2 QDs as signal amplification elements were successively labeled on the terminal of hairpin DNA probe. The target DNA detection was based upon the photocurrent change originated from conformation change of the hairpin DNA probe after hybridization with target DNA. In the absence of target DNA, the immobilized DNA probe was in the hairpin form and the anchored different sizes of CdTe-COOH and CdTe-NH2 QDs were close to the TiO2/CdS:Mn electrode surface, which led to a very strong photocurrent intensity because of the formation of the cosensitized structure. However, in the presence of target DNA, the hairpin DNA probe hybridized with target DNA and changed into a more rigid, rodlike double helix, which forced the multianchored CdTe QDs away from the TiO2/CdS:Mn electrode surface, resulting in significantly decreased photocurrent intensity because of the vanished cosensitization effect. By using this cosensitization signal amplification strategy, the proposed DNA assay could offer an ultrasensitive and specific detection of DNA down to 27 aM, and it opened up a new promising platform to detect various DNA targets at ultralow levels for early diagnoses of different diseases.

Ultrasensitive fluorescence detection of nucleic acids using exonuclease III-induced cascade two-stage isothermal amplification-mediated zinc (II)-protoporphyrin IX/G-quadruplex supramolecular fluorescent nanotags

A cascadic sensing system was developed for detection of DNA target at ultralow concentration by a combination of magnetic nanoparticles (MNPs) and exonuclease III (Exo III)-induced cascade two-stage isothermal amplification in the study. An ingeniously designed capture hairpin probe (CHP) that integrates target-binding and signal transduction sequences within one multifunctional design was assembled on MNPs. Upon sensing of the analyte nucleic acid, the hairpin probe on MNPs could be opened and stepwise removed by Exo III accompanied by the releasing of target DNA for the successive hybridization and cleavage process and the generation of bare signal transduction sequences of CHP as a new trigger for next circular reaction. The new DNA triggers initiate hybridizing with hairpin DNA probe that contains a partially “caged” G-quadruplex sequence (GHP), forming a duplex structure and liberating the active G-quadruplex structure. Then, Exo III digests the resulting duplex domain, leading to the recycling of new DNA trigger and simultaneously generating numerous ZnPPIX/G-quadruplex supramolecular complexes with the help of the zinc (II)-protoporphyrin IX (ZnPPIX), as an optical label for amplified fluorescence sensing event. Finally, numerous liberated cascade ZnPPIX/G-quadruplex supramolecular complexes give a remarkable fluorescence response. Because of two-stage autocatalytic recycling amplification and the specifically catalyzed formation of ZnPPIX/G-quadruplex supramolecular complexes, this newly designed protocol provides a high sensitivity with a detection limit of 0.75 fM, can discriminate mismatched DNA from perfectly matched target DNA, and gives low matrix effect due to using MNPs as the separation and amplification elements in the real samples. Therefore, it holds great potential for early diagnosis in gene-related diseases.

All-silicon multi-chip modules based on ultra-thin active pixel radiation sensors

The Semiconductor Laboratory of the Max Planck Society is designing and producing cutting edge radiation and particle sensors for experiments in basic science conducted by institutes of the German Max Planck Society and other international partners. One of the most challenging projects is the construction of so-called vertex detectors for experiments at high energy particle colliders like KEKB in Japan and the future International Linear Collider (ILC) as the next big international high energy physics project after the LHC at CERN, Geneva, Switzerland. Modern vertex detectors are pixelated position sensitive particle sensors based on highly specialized silicon technology similar to CMOS or CCD sensors for commercial optical applications. The goal is to measure the track of a secondary particle and extrapolate to the point of its origin. One of the main challenges for up-to-date vertex detectors is the requirement of low mass to minimize the effect of scattering of the traversing particle in the sensor material itself and the sensor support structures. We are developing ultra-low-mass sensors based on the DEPFET (DEpleted P-channel FET) pixel technology. DEPFETs are MOS transistors made on fully depleted detector grade silicon and combine the sensing and first signal amplification element in the same device. The thickness of the sensor is minimized and optimized for the best vertexing performance of the detector arrangement as whole. The detector is a cylindrical arrangement of sensor modules around the primary beam interaction point. The sensor module is a silicon based multi-chip module with the module substrate being the sensor wafer itself. There are three functional regions on the MCM: the 50 μm thin sensitive active pixel area with the DEPFETs in a two metal and two poly-silicon layer technology, the ‘end of stave’ with three metal layers (two Al and one Cu) where the read-out electronic is placed and the narrow frame in the same interconnect technology with the steering ASICs. Three types of ASICs are used: a mixed-signal ASICs as the analogue front-end and ADC, a digital data handling chip and a steering chip in HV-MOS technology for the row-wise addressing and clearing of the pixel matrix. There are 12 chips in total on the module, all bump-bonded to the substrate, about 3000 area array bumps in total. The finished module has 250 kPixels and is read out at a frame rate of 50 kHz via a wire-bonded flex cable. Our paper will describe the technology for the production of ultra-thin DEPFET sensors and the monolithically integrated support, testing challenges during production and their solutions as well as electrical, thermal, and mechanical properties of the assembled MCMs. An outlook will be given on how micro-channels for active cooling will be integrated in the current MCM concept.

Heterogeneous Optical Space Switches for Scalable and Energy-Efficient Data Centers

Optical space switches are key elements for the next generation of switching fabrics in backbone routers, high performance computing systems, and large data processing and storage systems. A number of architectures and alternative options for gating elements have been proposed, assessed, and implemented for a limited port count. The challenge is to further enhance the scalability and energy efficiency of space switches to support future traffic loads. This paper proposes a heterogeneous implementation of the space switches based on two different types of gating elements, namely semiconductor optical amplifiers (SOA) and Mach-Zehnder Interferometers (MZI). With respect to the existing homogeneous implementations, a higher energy efficiency can be achieved by minimizing the number of SOAs, but crosstalk is introduced by MZI. To reduce the power consumption while still guaranteeing adequate physical layer performance, the design of both Spanke and multi-stage architectures is optimized by strategically placing the different gating and amplification elements, and a physical layer analysis is carried out to validate the performance. The proposed heterogeneous implementation is able to achieve power savings up to 10% and 50% in the Spanke and multi-stage Benes architectures, respectively, with respect to SOA-based space-switch implementations. Moreover, an improvement of the physical layer performance is achievable in the Spanke architecture thanks to the different placement of the SOAs.

A label-free DNA hairpin biosensor for colorimetric detection of target with suitable functional DNA partners

The combination of aptamer and peroxidase-mimicking DNAzyme within a hairpin structure can form a functional DNA probe. The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. The presence of target triggers the opening of the hairpin to form target/aptamer complex and releases G-quadruplex sequence which can generate amplified colorimetric signals. In this work, we elaborated a universal and simple procedure to design an efficient and sensitive hairpin probe with suitable functional DNA partners. A fill-in-the-blank process was developed for sequence design, and two key points including the pretreatment of the hairpin probe and the selection of suitable signal transducer sequence were proved to enhance the detection sensitivity. Cocaine was chosen as a model target for a proof of concept. A series of hairpins with different numbers of base pairs in the stem region were prepared. Hairpin-C10 with ten base pairs was screened out and a lowest detectable cocaine concentration of 5μM by colorimetry was obtained. The proposed functional DNA hairpin showed good selectivity and satisfactory analysis in spiked biologic fluid. The whole “mix-and-measure” detection based on DNA hairpin without the need of immobilization and labeling was indicated to be time and labor saving. The strategy has potential to be transplanted into more smart hairpins toward other targets for general application in bioanalytical chemistry.

Label-free detection of aflatoxin M1 with electrochemical Fe3O4/polyaniline-based aptasensor

The selective detection of ultratrace amounts of aflatoxin M1 (AFM1) is extremely important for food safety since it is the most toxic mycotoxin class that is allowed to be present on cow milk with strictly low regulatory levels. In this work, Fe3O4 incorporated polyaniline (Fe3O4/PANi) film has been polymerized on interdigitated electrode (IDE) as sensitive film for AFM1 electrochemical biosensor. The immobilized aptamers as an affinity capture reagent and magnetic nanoparticles for signal amplification element have been employed in the sensing platform. Label-free and direct detection of the aptamer-AFM1 on Fe3O4/PANi interface were performed via electrochemical signal change, acquired by cyclic and square wave voltammetries. With a simplified strategy, this electrochemical aptasensor shows a good sensitivity to AFM1 in the range of 6–60ng·L−1, with the detection limit of 1.98ng·L−1. The results open up the path for designing cost effective aptasensors for other biomedical applications.

Recognition-driven layer-by-layer construction of multiprotein assemblies on surfaces: a biomolecular toolkit for building up chemoresponsive bioelectrochemical interfaces

The development of soft bioelectronic interfaces with accurate compositional and topological control of the supramolecular architecture attracts intense interest in the fast-growing field of bioelectronics and biosensing. The present study explores the recognition-driven layer-by-layer assembly of glycoenzymes onto electrode surfaces. The design of the multi-protein interfacial architecture is based on the multivalent supramolecular carbohydrate-lectin interactions between redox glycoproteins and concanavalin A (Con A) derivatives. Specifically, [Os(bpy)(2)Clpy](2+)-tagged Con A (Os-Con A) and native Con A were used to direct the assembly of horseradish peroxidase (HRP) and glucose oxidase (GOx) in a stepwise topologically controlled procedure. In our designed configuration, GOx acts as the biorecognition element to glucose stimulus, while HRP acts as the transducing element. Surface plasmon resonance (SPR) spectroscopy and quartz crystal microbalance with dissipation (QCM-D) results are combined to give a close representation of the protein surface coverage and the content of water in the protein assembly. The characterization is complemented with in situ atomic force microscopy (AFM) to give a topographical description of the layers assemblage. Electrochemical (EC) techniques were used to characterize the functional features of the spontaneously self-assembled biohybrid architecture, showing that the whole system presents efficient electron transfer and mass transport processes being able to transform micromolar glucose concentration into electrical information. In this way the combination of the electroactive and nonelectroactive Con A provides an efficient strategy to control the position and composition of the protein layers via recognition-driven processes, which defines its sensitivity toward glucose. Furthermore, the incorporation of dextran as a permeable interlayer able to bind Con A promotes the physical separation of the biochemical and transducing processes, thus enhancing the magnitude of the bioelectrochemical signal. We consider that these results are relevant for the nanoconstruction of functional biointerfaces provided that our experimental evidence reveals the possibility of locally addressing recognition, transduction and amplification elements in interfacial ensembles via LbL recognition-driven processes.

G-Quadruplex-based DNAzyme for colorimetric detection ofcocaine: Using magnetic nanoparticles as the separation and amplification element

The appearance of the aptamer provides good recognition elements for small molecules, especially for drugs. In this work, by combining the advantages of magnetic nanoparticles (MNPs) with colorimetric drug detection using hemin-G-quadruplex complex as the sensing element, we report a simple and sensitive DNAzyme-based colorimetric sensor for cocaine detection in a 3,3,5,5-tetramethylbenzidine sulfate (TMB)-H(2)O(2) reaction system. The whole experimental processes are simplified. Cocaine aptamer fragments, SH-C2, are covalently labeled onto the amine-functionalized MNPs. When the target cocaine and another cocaine aptamer fragments (C1) grafted with G-riched strand AG4 (i.e. C1-AG4) are present simultaneously, the C2 layer on MNPs hybridizes partly with C1-AG4 to bind the cocaine. The C1-AG4 can be combinded with hemin to form DNAzyme which can effectively catalyze the H(2)O(2)-mediated oxidation of TMB, giving rise to a change in solution color. Importantly, using MNPs as the separation and amplification elements could effectively reduce the background signal and the interference from the real samples. A linear response from 0.1 μM to 20 μM is obtained for cocaine and a detection limit of 50 nM is achieved, which provides high sensitivity and selectivity to detect cocaine.

Aptamer-Au NPs conjugates-accumulated methylene blue for the sensitive electrochemical immunoassay of protein

In this paper, we combine the advantages of aptamer, nanomaterial and antibody to design an electrochemical sandwich immunoassay for the ultrasensitive detection of human immunoglobulin E (IgE) by using methylene blue (MB) as electrochemical indicator. The sandwich structure is fabricated by using goat anti-human IgE as capturing probe. Aptamer-Au nanoparticles (NPs) conjugates are used both as a sandwich amplification element as well as an accumulation reagent of MB. Once the aptamer-Au NPs conjugates specifically bind to electrode surface, MB molecules are accumulated on its surface by the specific interaction of MB with G base of aptamer-Au NPs conjugates. Therefore, with the increase of human IgE concentration, more aptamer-Au-NPs conjugates are bound, and thus, more MB molecules are accumulated. A good linear relationship is obtained for the detection of human IgE over a range of 1-10,000 ng/ml with a lowest detection limit of 0.52 ng/ml. In addition, by using BSA, human IgA and human IgM as contrast, the excellent specificity of this sensing system for the detection of human IgE is also demonstrated.

Theoretical analysis of pattern effect suppression in semiconductor optical amplifier utilizing optical delay interferometer

The ability of an optical delay interferometer (ODI) to suppress the pattern effect that is inherently present in a straightforward, solitary semiconductor optical amplifier (SOA) whose dynamic response is slower than the period of its driving high-speed return-to-zero (RZ) data signal is theoretically investigated. For this purpose an existing comprehensive model that simulates and links the operation of these two elements is methodically applied to their concatenated configuration. In this manner an extensive set of curves is numerically obtained, which allow to analyze and assess the impact of the input pulse energy and width as well as of the SOA carrier lifetime, linewidth enhancement factor and small signal gain on the amplitude modulation of the transmitted sequence at the output of each one of these block units. Their thorough study and interpretation reveals that the employment of the ODI can significantly reduce the value of this quality metric resulting from a single SOA only. The main offered benefit, however, is that any technical restrictions regarding the involved critical parameters can be considerably relaxed while at the same time their useful operational range can be extended. These important findings highlight the necessity of placing this passive device after the SOA and exploiting it in order to effectively alleviate the detrimental pattern-dependent degradation. This fact in conjunction with its overall practicality renders it a promising candidate for enhancing, within the frame of the proposed scheme, the performance of SOAs that are employed as pure amplification elements in fiber-optic communication systems and networking applications.

Precision sensor assembly for rotating members in a machine tool

A precision sensor assembly for rotating members in a machine tool comprises a rotor unit ( 16 ) rigidly fixed to a rotor portion ( 2 a ) of the machine tool and including a sensor ( 5 ) for detecting vibrations produced by the operation of the machine tool, the sensor ( 5 ) comprising a piezoelectric sensitive element ( 6 ) and members ( 7, 8 ) for mechanical amplification of the vibrations. The members ( 7, 8 ) comprise at least one resonant system composed of an elastic element ( 8 ) and a counter-mass ( 7 ) acting on the piezoelectric sensitive element ( 6 ). The rotor and stator units ( 16, 17 ) comprise inductively coupled transmitting and receiving elements ( 10, 11 ) for transferring the signals from the piezoelectric element ( 6 ) contactless to the stator unit ( 17 ). The stator unit ( 17 ) may include an electric amplifier ( 13 ) for further amplifying the transmitted signals.

Amplification processes in networks with intermediate storage of information

Model of a single channel mass service system is suggested and described that allows considering it as an amplification element in information network and using tensor method for its analysis without limitations on information load. Analytic expressions of the main amplification characteristics for a single channel system M/M/1 are obtained.

164 ホタルの集団同期発光における過渡的なウェーブ現象

This paper describes a transitional wave phenomenon in synchronous flashing of fireflies. We used self-excited oscillator, consists of amplification element, saturation element and phase delay element. To simulate a transitional wave phenomenon, the self-excited oscillator simulated the firefly shouldn't be late from the detection of the flashing of other self-excited oscillator. The period of self-excited oscillator in the transient state depends on strength of own flashing and changes. Strengthening strength of own flashing, perceived the flashing of other self-excited oscillators, the timing of flashing shifts and withdraws by correcting it at a constant period. This is a transitional wave phenomenon.

406 ホタルの集団同期発光を模擬した相互引込みの実現(同期化・パターン形成,OS-6 パターン形成現象と複雑性)

This paper describes the frequency entrainment that simulates synchronous flashing of fireflies. We used self-excited vibrator, which consists of a phase delay element, an amplification element, and a saturation element. Although self-excited vibration generated in self-excited vibrator grows gradually, amplitude is stopped by saturation at a limited value. Then the saturation element is acted as a variable gain from which a gain changes with the sizes of an input. The transient state and steady state of synchronization which are produced in self-excited vibrator group are investigated, and it found out that it was similar with synchronous flashing of a firefly.